Diverse energy standards have been drawn up by government authorities in order to spare the environment. One of these is the Energy Performance Standard (EPS) which expresses the energy efficiency of a new dwelling in the so-called Energy Performance Coefficient (EPC). The EPC represents the energy consumption of a building relative to a similar reference building described in the standard (for dwellings and residential buildings in the Netherlands this is currently NEN 5128/2001). This EPC is calculated on the basis of the building properties (insulation value of walls, floors, glazing and so forth) and installations (for instance solar collectors, ventilation systems and heating). The lower the number, the greater the energy efficiency of the building. The Energy Performance Coefficient (EPC) can thus be deemed as a measure for the (average) energy quality of a building, including the technical installations. The level of the EPC is laid down in the Building Act in the form of a minimum EPC requirement, which is set at 0.8 as of Jan. 1, 2006. All newly built houses must comply with this maximum allowed EPC.
Energy consumption is determined on the basis of, among other factors, the energy consumption for heating, hot tap water, pumps, cooling, fans and lighting. If a newly built house does not achieve an EPC of 0.8, this means that additional measures such as solar panels and/or triple glazing must be applied, and this can markedly increase the cost of building a house.
One method of making efficient use of energy and environment is to reuse lightly contaminated water. Instead of mains water, which is treated with considerable effort and at a great cost in wastewater purification plants, less clean non-potable water can be used for some applications, such as, for instance, flushing the toilet. It is thus possible to envisage the use of collected rainwater and the reuse of lightly contaminated bath and shower water, also referred to as greywater. This saving of water furthermore results in a proportional reduction in the stress on the sewage system.
The use of the relatively warm greywater also has another favorable effect on the Energy Performance Coefficient (EPC): there is a reduction in the “cold source” which normally occurs when cold mains water is fed into and stored in a cistern. The system itself moreover also has a favorable effect on the EPC in the form of heat generation.
Netherlands Patent No. 1011371 describes a reservoir for greywater with a feed for greywater and a discharge connected to a greywater user such as a toilet or the like. The reservoir is provided with an outlet which connects to the sewer and which is provided with a valve to be opened at regular intervals by a time clock. Regular disposal of greywater prevents odor nuisance being caused.